Abstract
Currently, millions of tons of steel are produced worldwide. This has become a serious economic and environmental challenge because the ores used for steel production are nonrenewable resources and the production generates huge amount of waste. In this study, we identified and investigated the ability of bacteria from steelmaking waste with low and high zinc concentration to promote leaching of zinc, when enriched by acidic (pH 2) culture conditions. The bioleaching assays indicated removal of Zn, as in chemical leaching. Bacterial communities from crude and enrichment culture wastes were characterized by the 16S rRNA gene. Phylogenetic analysis of the generated clone libraries revealed predominance of Proteobacteria and Firmicutes. The Actino- bacteria, Bacteroidetes, Cyanobacteria, and Deinococcus-Thermus phyla were also encountered. The clones were most closely related to cultivable heterotrophic bacteria. Different genera were identified including iron redox cycling and leaching bacteria such as Chromobacterium, Aeromonas, Escherichia, Bacillus, and Ochrobactrum. These data add significant new information on bacteria which survive in extremely acidic conditions. They are distantly related to typical acidophiles responsible for the leaching process, which makes them good candidates for future studies on metal bioleaching.
Highlights
Steelmaking activities have been intensive during the 20th and 21st centuries, resulting in the generation of huge amounts of waste including the presence of metals such Zn, Cu, and Cr [1]
We identified and investigated the ability of heterotrophic bacteria from steelmaking wastes to survive in acidic conditions and to promote leaching of zinc
The wastes studied were crude thin sludge waste (TS), constituted by fine solid particles resulting from the Linz-Donawitz converter, and crude sludge from treatment of electroplating effluent waste (STEE), both of which were released into the environment three days before sampling
Summary
Steelmaking activities have been intensive during the 20th and 21st centuries, resulting in the generation of huge amounts of waste (approximately 700 kg of waste per ton of steel produced) including the presence of metals such Zn, Cu, and Cr [1]. Most of the waste is being left without proper management all over the world and without any management whatsoever in Brazil and perhaps in other countries as well. The release of these wastes to the environment leads to contamination and consequent human exposure to the metals present in these rejects. The waste generated by this industry can no longer be ignored. First steps towards solutions for its management would be the search for suitable technologies to enable the removal of metals from these wastes
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